In recent years, research and development related to organic electroluminescence elements (hereafter, “organic EL elements”) has been advancing. Organic EL elements are current-driven light-emitting elements that use electroluminescence of organic light-emitting materials. Organic EL display panels in which organic EL elements are arranged on a substrate are widely used as display devices using organic EL elements. An organic EL element in an organic EL display panel may, for example, be composed of a thin-film transistor (TFT) substrate, an anode composed of metal such as Al, a light-emitting layer composed of organic light-emitting material, and a cathode composed of light-transmissive material such as indium tin oxide (ITO), layered in the stated order. Further, such an organic EL element may include, as required, a hole injection layer, a hole transport layer, an electron injection layer, an electron transport layer, a sealing layer, etc.
Among methods for manufacturing a light-emitting layer in an organic EL display panel are a method of using vacuum deposition and a printing method of applying organic material ink containing trace amounts of organic light-emitting material dissolved in solution. A light-emitting layer can be formed by a simpler manufacturing apparatus when using such a printing method than when using a vacuum deposition method. Thus, there is an advantage that such a printing method can also be used when manufacturing a large organic EL display panel.
The following is a description of a conventional method of forming a light-emitting layer by a printing method using inkjets. First, a bank layer composed of material including a liquid-repellent component is formed on a substrate. Further, sub-pixel regions are formed as a plurality of openings in the bank layer. Further, organic material ink is applied into each sub-pixel region, and by drying the organic material ink light-emitting layers are formed within each sub-pixel region (see Patent Literature 1). Light-emission colors of adjacent light-emitting layers are different colors from among red (R), green (G), and blue (B). Further, material for the light-emitting layers is different for each light-emission color.